Madison, WI Environmental Rules: Flood Zones (2026)

Madison lies along the Yahara River watershed, including the four lakes Mendota, Monona, Waubesa, and Kegonsa. FEMA Flood Insurance Rate Maps (FIRM) show Special Flood Hazard Areas (SFHA) along the Yahara River, Starkweather Creek, Pheasant Branch, Wingra Creek, and low-lying lakeshore areas. Zone AE (1% annual chance, regulatory floodway and floodway fringe) covers most lakeshore and riverine areas; Zone X shaded covers the 0.2% annual chance (500-year) floodplain. Federally-backed mortgages in Zone AE require flood insurance. Madison General Ordinances 28.149 implements Wisconsin NR 116 floodplain management: new residential structures prohibited in the floodway; structures in the floodway fringe must have lowest floor elevated 2 feet above the base flood elevation (Wisconsin requires 2 ft freeboard, more stringent than FEMA's 1 ft). Fill in the floodway prohibited. Substantial improvements (50%+ of value) trigger full compliance. The 2018 flood events on the Yahara chain highlighted vulnerabilities; the city participates in FEMA Community Rating System for discounted premiums.